The present invention relates to an improved process for concentrating elemental lead in crude lead bullion, and, more particularly, to an improvement in such a process whereby sodium or a sodium-containing reagent is introduced into the molten crude bullion and the crude bullion contains less than about 1.3% by weight of sulfur as sulfide, the improvement comprising introducing iron or an iron-containing sulfide reagent and an amount of previously isolated copper speiss into the crude bullion either prior to or substantially simultaneously with the sodium whereby formation and separation of the matte, speiss and lead bullion equilibrium phases is enhanced. The isolated phases are (1) a low lead, low arsenic matte phase comprising primarily copper sulfide and sodium sulfide; (2) a low lead, high copper, high arsenic and iron speiss phase; and (3) a high lead, low sulfur, low arsenic, high silver lead bullion phase.
U.S. Pat. No. 4,404,026 describes a method for introducing sodium into molten crude lead bullion followed by controlled solidification to separate a matte phase and a copper speiss phase from the lead bullion phase. However, the ability of sodium to cause such beneficial separation of the equilibrium phases declines as the sulfur content of the crude bullion declines, usually to values below about 1.3% by weight. The mass of equilibrium phases formed can be too small for effective separation.